Manufacturing red lead



Get. 13,1925- 5 6,820

H. HOCKING MANUFACTURING BED LEAD Filed Aug. 5, 1924 Patented Oct. 13, 1925.

UNITED STATES 1,556,820 PATENT OFFICE.

HENRY nocxmo, or nonarnsgr, HUNGARY, assrenon or ONE-HALF 'ro ORION- REZ- KOEO-ES m'izeALIcoYAn nnszvnnyransasao, or nonarnsr, HUNGARY.

MANUFACTURING RED LEAD.

Application filed August 5. 1924. Serial No. 730.298.

To all whom it may comcem:

Be it known that I, HENRY HOGKING, a subject of the King of Great Britain, residing at Budapest, Hungary, have invented certain new and useful Improvements in Manufacturing Red Lead, of which the following is a specification.

My invention relates to an improved process for manufacturing red lead in a single operation from metallic lead.

The difficulties in carrying out the old processes of this kindin a manner satisfying practical requirements arise from the. fact that when oxidizing metallic lead, the layer or incrustation of oxide produced on the surface of the metallic lead particles prevents such particles from being oxidized or at least retards considerably the oxidizing process.

Now, in order to overcome the said difliculties, in practice special means are usually applied adapted to stir or cut the bath of liquid lead during oxidation whereby constantly new surfaces of metallic lead are exposed and subjected to the direct action of V the oxidizing gases.

The lead-oxide produced in this way, however, generally constitutes a leafy mass still containing considerable quantities of metal- 80 lic lead which mass is not suitable for homogenously oxidizing further to the second stage to get red lead of marketable quality, but has to be prepared for the said second oxidizing stage in a special way by applying first a separate milling or grinding, and then a separate washing operation to convert the leafy lead-oxide mass into a fine powder free from lead particles.

Now, according to my invention market able red lead of righ quality may be obtained from metallic lead by a single operation satisfying all requirements as to economy and output. This is accomplished by oxidizing v. .metallic lead heated under pressure to a'tem'perature above its melting point through the action of oxidizing gases while it is simultaneously subjected to a milling or grinding action.

Owing to the simultaneous and combined oxidizing action under pressure and milling or grinding the material while it is being oxidized, the formation of surface oxide incrustation on metallic lead particles becomes practically or wholly impossible because any oxide formed is almost instanta neously crushed to powder sufficiently fine to be immediately oxidized to the second stage resulting in the formation of red lead. Moreover, owingto the continuous milling or grinding acting upon thematerial while it is being oxidized the red lead is attained directly from the oven in a highly divided powdered form not requiring any separate subsequent operation to get a commercial quality of marketable red lead.

I am aware of the -fact that it is well known per se to roast lead-oxide or white lead to red lead under pressure. This way, however but the second stage of oxidizing lead may be carried out which starts from lead-oxide or white lead previously brought to a powdered form by means of a separate grinding operation and then freed from metallic lead particles by a separate washing operation following the grinding whereas according to my invention metallic lead may be converted to red lead directly without separate grinding and washing operations between the two oxidizing stages as heretofore found generally necessary.

My invention will be readily understood from the following description taken in connection with the accompanying drawing in which Figure 1 is a vertical cross section showing apparatus in which my invention can be carried into effect, the section being taken on line 1-1 in Figure 2, and Figure 2 is a vertical longitudinal section taken on line 2-2 in Figure 1.

My apparatus consists of a ball milla provided with hollow axial projectin shafts b rotatably mounted within the com ustilon chamber of a furnace 0. One of the hollow axial projections b is provided with a fluid tight cover d and serves as a channel for admittin a charge to the mill while the other ho low axial projection 12 communicates with a pipe 6 detachably connected to a convenient source is of oxidizing gas such as air, or the like under pressure.

As grinding means I prefer to use iron balls 9 although any other form of rolling bodies may be used if found desirable.

To enable the'ball mill a to be rotated a pulley f is provided on one of the axial projections b, said ulley being connected to any convenient klnd of power (not shown).

The operation isas follows g The ball mill is charged through the channel b with solid or melted metallic lead whereupon the said-channel is cloud by meags 8f tlile coveii d. The1 mill (is then rotate yte ue an 0x1 izing gas under ressurd is mfinitted. Within the ball mi I prefer to maintain a ressure of about 4 to 6 atm., and should t e pressure for any reason, chemical binding or leakiness for instance, -fall'below this I raise the pressure again by admitting an additional suppl of the oxidizin as. The heating of t e exteriorof thefiial mill is regulated in such a manner that the char e therein is heated to a temperature above t e melting point of metallic lead, preferably to about 300-350? C. In continuin the o eration as described for about'five Iiours t e metallic lead is oxidized to red lead in finely divided powdered form.

It is believed that in comparison with the lmown two stage processes the single stage process according to my invention will result in a considerable saving of cost and time. The two sta e processes as a rule require, inclusive of the separate grinding and washing operations, 144: workin hours, as well as a considerable number 0 men to carry out the different operations at diiferent places and in difierent machines, whereas the process according to myinvention will require but five hours to produce directly from metallic lead, marketable red lead, the handling of the material bein limited to the charging and discharging o the ball mill, and the necessity for transporting intermediate products to diflEerent urnaces and machine as heretofore will be obviated. As a further result thereof the workcosts of the whole plant will be considerably smaller than those for the two stage processes. The amount offuel necessary to oxidize metallic lead to red lead will be a mere fraction of the fuel used with known processes, and the chemical reaction will go on without an loss whatever and practlcally with quantltative yield. A further advantage resulting from my one stage process is that workmen will not be sub ected to the danger of lead poisoning since the lead charge is enclosed in one and the same hermeticall sealed chamber until completely oxidize to red lead.

Although I have described my apparatus in connection with my one stage rocess for making red lead, it is obvious t at I may charge my ball mill if desired with lead oxide or white lead' to which will also be maintaining within the said vessel a raised 1 pressure by means of an oxidlzlng gas under pressure, and rotating the said vessel while pressure tig t vessel, simu taneously the charge therein is being heated to a temperature above the melting point of lead.

In testimony whereof I aflix my signature. I

HENRY HOCKING. 

